In recent years, with surging traffic in a communication network and growing number of services performed in the network, a lot of technologies for establishing a virtual network additionally in the communication network have been developed. There is a VLAN (Virtual Local Area Network) disclosed in the non patent literature 1 as one of typical methods for establishing such a virtual network.
In a network in which a plurality of servers are connected like a large-scale data center, virtualization is generally realized using a VLAN-ID which is an identifier of each VLAN in addition to an IP (Internet Protocol) address for each usage of the server. By this virtualization, a network is designed so as not to be influenced in communication even if an identical IP address is used among a plurality of servers.
However, there is a limitation in the number of VLAN-ID to be allocated, and its number is at most 4,096. When a VLAN is used in a large-scale network, if the VLAN-ID is assigned for each IP address of a server by a method as mentioned above, the number of VLAN-ID becomes insufficient. As a result, there is a problem that sufficient number of the virtual networks cannot be provided.
Technology for solving such problem is disclosed in the patent literature 1. In the patent literature 1, a VLAN domain ID which is another identifier different from the VLAN-ID described in the non patent literature 1 is newly proposed. In the patent literature 1, it describes a technology that a switching hub identifies a VLAN to which a received frame belongs, by combining the VLAN domain ID and the VLAN-ID.
In the patent literature 2, it describes a technology that a source MAC (Media Access Control) address is stored in a MAC address learning table associated with VLAN tag information when a packet has been received.